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Solar inverter failure checklist
A checklist for O&M, EPS and OEM field technicians: isolate first, match the symptom to the likely section, and record what you need before you send a unit for repair. Use it on site, then print it or keep it on your phone.
Before you open or power any inverter
Isolate both sides
Switch off the AC grid side and isolate the DC input from the strings. Use the isolators and follow your site's lock-out procedure.
Wait for discharge
DC-link and capacitor banks can hold energy after power is removed. Wait for the discharge time stated in the OEM manual, then check.
Verify the unit is dead
Test for voltage at the terminals before touching any part, and use the correct personal protective equipment.
Record before you touch
Photograph the nameplate, the display, the fault codes and the event log. Note the time the fault began.
Match the symptom to the likely section
These are starting points for diagnosis, not conclusions. Confirm each one with measurements and the OEM manual.
| Symptom | Check first | Likely section |
|---|---|---|
| No display, no power-up | DC input, fuses and connections; auxiliary supply output | Auxiliary power supply, control board supply |
| Grid fault or no grid connection | Grid voltage and frequency at the terminals; relay and contactor operation | Grid interface: relays, contactors, voltage and current sensing |
| Earth fault or insulation alarm | Cable insulation and moisture; DC-side earth; RCMU indication | RCMU sensing circuit and its supply |
| Output derating or repeated trips | Heatsink temperature, fan operation, DC-link condition | Power stage, DC-link capacitors, cooling |
| Communication fault | Cabling, settings and the communication board's LEDs | Communication circuit on the control board |
| Intermittent faults | Connectors, cracked solder joints, and whether the fault follows temperature | Connectors, board joints, thermal stress |
What to record before you send a unit for repair
A complete record lets us confirm the repair route quickly and avoids a second round of questions.
- Make, model and serial number, with a nameplate photo
- Fault codes with their dates and times
- Event log export, if the inverter can provide one
- DC input and AC output readings taken at the time of the fault
- Site environment, such as temperature, humidity and any water ingress
- When the fault began, and whether it has happened before
Send the record, and get a free board evaluation
Send the record and the nameplate photo. We reply with the likely faulty section and whether component-level repair is practical for the unit. See how the repair works.
This checklist is for guidance. It does not replace the OEM manual or your site's electrical safety rules.